The present invention relates to rotary or disc mowers of a type including an elongate cutterbar, and more particularly relates to such a cutterbar including a fluid-tight gear housing adapted for holding lubrication fluid for the gears contained in the housing.
The idea of using a cutterbar drive gear housing as a gear lubrication fluid reservoir is well known in the art. Both underfilling and overfilling the cutterbar with lubricant will result in gear damage, damage through underfilling resulting because of the gears becoming starved for lubrication and running dry; and damage through overfilling resulting because the gears churn and overheat the fluid which causes it to break down and lose its lubricity. Of course, operation of the gears in a bath of lubricating fluid is also not desirable because of the power loss attendant with such operation.
U.S. Pat. No. 4,539,797, granted 10 Sept. 1985, discloses a cutterbar including a housing which is substantially rectangular in cross section and having a depth only slightly greater than that of a series-arranged spur gear train contained therein for driving cutting units carried by the housing. Thus, the volume of the housing which is available for containing lubricant is relatively small which has the disadvantage of making the cutterbar quite sensitive to both underfilling and overfilling of lubricant. Although the patent features a way of detecting whether or not sufficient lubricant is contained in the cutterbar, the method of checking lubricant level is not very convenient or simple since it involves placing the cutterbar on a relatively level area, elevating one end of the cutterbar a predetermined amount and then removing a fill plug from the elevated end to see if the lubricant level is up to the fill plug orifice, such a level of lubricant being an indication of a sufficient amount. While this may be an effective way of determining if enough lubricant is present, it has the disadvantage of not effectively preventing overfilling of the cutterbar since an operator is liable to think that the cutterbar is properly filled if lubricant is present when the fill plug is removed when in fact the cutterbar may be overfilled.